For the purpose of interventions, for example as applied in catheter labs under fluoroscopy when treating coronary stenoses, it is known to visualize vessel structures and devices advanced inside the vessel structures. Hereby, firstly a contrast agent is injected via a catheter and an X-ray examination apparatus records an angiographic sequence, which is also called an “angiogram”, that shows the vessels that are radio-opaque when filled with the contrast agent. Secondly, during the intervention, for example a flexible, partially or fully radio-opaque guide wire is advanced to affected vascular structures and by means of low-dose fluoroscopic X-ray surveillance the guide wire is visualized, which is referred to as “live images”. By means of an overlay technique the angiogram and live images are overlaid so that a medical image containing the vessel structures and the device at the same time can be created. This technique is referred to as “road mapping” that allows for the hand-eye coordination while advancing the device, e.g. a guide wire.
For the navigation of devices within the vessels a subjective visual fusion of the static angiogram and the live fluoroscopy images is required. Since the angiogram contains a number of distinct images that are shifted relative to each other and are acquired at different times, e.g. over one complete cardiac cycle and the vessels in the live images are moving, an accurate method for this road mapping is mandatory.
A way to achieve the road mapping procedure is to choose an object-based process, wherein firstly arteries are extracted from the angiogram, yielding a cardiac cycle of artery tree images. A targeted object in the live images is chosen as a spatial reference. Secondly, the artery tree images are shifted and superimposed to the live fluoroscopic images according to the targeted object in order to better cover the live interventional devices.